1. Field of the Invention
The present invention relates to a temperature compensation method for a microwave oven, and more particularly to a method capable of compensating for a detected temperature error of a food which is caused by electromagnetic wave noise when a heating operation of a microwave oven is controlled by an infrared sensor.
2. Description of the Prior Art
A conventional microwave oven (hereinafter "MWO") finishes cooking by stopping a heating operation when a detected temperature from an infrared sensor reaches a cooking temperature after the heating operation starts. However, it is difficult to discriminate whether the temperature detected from the infrared sensor is the correct temperature of the food or a temperature caused by electromagnetic wave noise. Therefore, in a conventional MWO, at the moment the temperature detected from the infrared sensor reaches cooking temperature, cooking is stopped immediately; thus, the food may not be sufficiently cooked to a desired level.
FIG. 1 illustrates a block diagram showing a hardware system of a MWO in general.
The MWO comprises an opening 4 at the upper part of a cooking chamber 1 and an infrared sensor 5 for detecting the temperature of a food 7 placed in the cooking chamber 1 through the opening 4. Also, the MWO comprises a heating part 3 for generating a microwave based on the temperature detected from the infrared sensor 5. The MWO also includes a controlling part 6 for controlling the overall operation of the system.
Moreover, a turntable driving motor 8 being controlled by the controlling part 6 is installed at the lower part of the cooking chamber 1. A turntable 2 is installed inside of the cooking chamber 1. The turntable 2 is rotated turned by the rotation of the motor 8 mounted at the upper part of the motor 8 axis. Cooking stuff 8 is placed thereon.
The controlling part 6 controls the heating part 3 and the driving of motor 8 after a heating start key is operated. As shown in FIG. 2, the controlling part 6 comprises:
A key inputting part 6a for predetermining the cooking temperature suitable for a desired food, or inputting the heating start signal; a predetermined temperature storing part 6b for storing the predetermined cooking temperature; a detected temperature storing part 6c for temporarily storing the temperature detected from the infrared sensor 5; a displaying part 6d for displaying a simple message, i.e. the predetermined temperature and the detected temperature with liquid crystal display; and a output controlling part 6e for controlling the output by comparing the predetermined temperature with the detected temperature.
That is, the controlling part 6 disseminates the detected temperature by a signal detected from the sensor 5, and then operates the heating part 3 to the extent that the detected temperature approaches the predetermined temperature and controls the heating part 3 until cooking is completed.
Food 7 is heated by a microwave emitted from the heating part 3. The turntable 2 rotates such that the emitted microwave evenly impinges the food 7 when the heating part is operated.
The control operation of the conventional MWO including the above system is described in detail as follows.
The user puts food 7 on the turntable 2, predetermines a proper cooking temperature through the key inputting part 6a, and accuates the heating start key. The predetermined cooking temperature is stored in the predetermined temperature storing part 6b.
The output controlling part 6e, as the heating start key is accuated, operates the heating part 3 and the turntable driving motor 8. Simulataneously, a microwave is emitted from the heating part 3 in order to heat the food 7. As the heating part 3 is operated continually, the temperature of food 7 rises.
The infrared sensor 5 detects through an opening 4 the food temperature placed in the cooking chamber 1. The detected temperature is temporarily stored in the detected temperature storing part 6c.
The output controlling part 6e reads the temperatures stored in the detected temperature storing part 6c and the cooking temperature stored in the predetermined temperature storing part 6b, and compares both of them. Then, the output controlling part 6e heats food 7 by continuously operating the heating part 3 to the degree that the detected temperature comes up to the cooking temperature. As the temperature detected from the sensor 5 reaches the cooking temperature, the output controlling part 6e stops the operation of the heating part 3.
Therefore, the automatic cooking controlling method for a conventional MWO completes a cooking operation when the predetermined cooking temperature is detected through the sensor 5.
According to the temperature controlling method for the conventional MWO, there is a slight difference between the detected temperature value of food detected from the sensor 5 and the real temperature value of food. This is caused by high frequency while the heating part oscillates. That is, the detected value of the infrared sensor 5 does not coincide with the value of predetermined cooking temperature due to high frequency, generated by an oscillation of the heating part 3. As a result, the conventional control method for the conventional MWO fails to accurately cook a food to a predetermined temperature due to the above-discussed disadvantages.